Role based system and device for command and control

ABSTRACT

A system and device for enabling tracking and communication between units in a team, typically used for military or rescue operations. The system, known as Command and Control System, has a handheld central unit with a display for showing positions of team units and portable team units having GPS, compass and radio communication function for sending and receipt of positions and alarms and for receiving text messages, a display for showing own positions and bearings. The units have the ability to send data directly or relayed to each other. Each unit can be assigned one or more roles and can send or receive messages that instruct actions like, deletion of vital information or control of power consumption.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Submission Under 35 U.S.C. §371 for U.S. NationalStage Patent Application of International Application Number:PCT/NO2009/000196, filed May 26, 2009 entitled “ROLE BASED SYSTEM ANDDEVICE FOR COMMAND AND CONTROL,” which claims priority to NorwegianPatent Application Serial No. 20082556, filed May 30, 2008, the entiretyof both which are incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

n/a

FIELD OF THE INVENTION

The present invention relates to a system and a device for wirelesscommunication and more particularly to a communication system consistingof a central unit and portable team units with positioning capabilityand the ability to send and receive information between each other. Formilitary and rescue operations such systems, or groups of such systems,are often called Command and Control Systems (abbreviated to CCS orC2S).

BACKGROUND OF THE INVENTION

Current portable wireless communication terminals for military and fielduse have the ability to communicate with other similar devices over alarge area and have map systems that show an abundance of informationthat can be shared. They also have the ability to send audio messages tothe other terminals in form of peer to peer voice messages like thesimilar “walkie-talkie” technology.

However there are situations where large complex systems with maps andaudio communication are not favorable, in certain field situations thereare advantages to having a communication terminal that can be operatedsimply and that does not show unnecessary information; there are alsocertain situations where it is an advantage to communicate via textmessages and not through audio messages, like in areas with a high noiselevel e.g. during an emergency, or a catastrophe, or areas where thereis an advantage to keep a low noise level e.g. in a military operation.In these situations it is crucial that the unit is easy to operate andthat the information shared by the different terminals does not reachthe wrong person(s). In these situations it is also favorable to havethe ability to communicate with all the other team units. In certainsituations like in a rescue operation or in a military operation it isalso an advantage to assign the different units one or more roles thatcan be displayed to the other units, reflecting the unit's tasks. Thisrole must be possible to change, both from the unit itself, or fromunits with a relevant role. E.g. a team leader can assign roles to itsteam members, but if the team leader is taken out of operation anotherunit must be able to take the role as team leader.

It is known from FFI Fakta(http://www.mil.no/multimedia/archive/00086/Faktark-NORMANS-KKI-_(—)86445a.pdf)that a system designated “Normans KKI” and “Normans ledelse” includes aunit (KKI) to be placed and integrated by wire on a soldier's dress inorder to make information about positions of the soldier and designatedteam members show up on a display of the unit. The unit contains adigital magnetic compass and a GPS and also a simple message functionenabling for example alarm messages. Passive sensors can be coupled tothe unit. The “ledelse” unit is a handheld unit that shows the positionsof all soldier units displayed on a digital map giving the leader anoverview of his team. The “ledelse” unit is supplied with software forinteractive planning with the units of the soldiers. Marching routes,way points or other battle related information can be put into thedigital map. Also, active sensors can be coupled to the “ledelse” unitand information from passive sensors on the soldiers' units can becollected. The message functions of the “ledelse” units allow forsending and reception of maps, text, orders, alarms and positions.

The systems available at the present like the one in US 2006/0238331 A1shows a communication unit mainly for military use that has a GPS basedmap interface displaying the location of other team units. Thisinformation is shared between the different team units by radiocommunication via a central unit that receives the information,organizes it and sends it back out to the different team units in thesystem in a strict hierarchy, using a master-slave configuration. Thedifferent team units can also receive audio messages either from thecentral unit or from each other. These team units have in addition tobiosensors that monitors the pulse, temperature and blood pressure alsoabilities for iris scan of the user and a credit card chip for economicsettlement.

Further it is known from U.S. Pat. No. 6,898,526 B2 a communicationterminal system intended for hunters that has a GPS based map system anda radio communication device for communicating your position to acentral unit, the central unit sends the location of the different teamunits to each team unit. The information is shown on a map interfacewith a compass bearing, the team unit then further communicates with theweapon in the form that it always knows where it is pointing and canstop the weapon from firing in the direction of other team units. Thissystem does not have the ability to communicate any other informationthan the location information received from the GPS unit.

It is also known from U.S. Pat. No. 6,373,430 B1 a portable team unitwith GPS and radio that communicates the location information from theGPS with one or more other equal team units. The location information issent over the radio link to the other team units. This information isshown in a map interface so that everybody in the system can see wherethe others are by showing a unique identification tag for each teamunit.

U.S. Pat. No. 6,456,938 B1 teaches a system for navigation at a golfcourse, having a screen for showing a map of the course. The system hasmessages, and can show distances and bearings. The units may communicatedirectly, but cannot relay messages, nor show other player's position.

US2005/0001720 A1 and US2008/096519 A1 both teach systems that tracksmobile terminals and where a unit can have a role as e.g. “leader”.

Neither of these documents have a solution to the problem of avoiding athird party from using a lost or compromised unit, or that a unit may bediscovered, disturb other communications or use too much battery becauseit transmits with unnecessary high power.

SUMMARY OF THE INVENTION

The system of the present invention consists of control and team units.In a preferred embodiment there is one control unit, typically used bythe team leader, and several team units that all have roles. Thepositions of all team members are indicated on the displays, and theunits can communicate with data messages directly or relayed with oneanother. Communication to other teams or to a headquarters is in normalsituations done from the control unit only using another tacticalcommunication system. In a preferred embodiment, all communication isencrypted, using asymmetric encryption to distribute a key for symmetricencryption to be used for a period.

The Team and Control Units

The unit of the present invention is a small communication unitspecifically developed for soldiers, first responders such as firefighters and the like. It has integrated radio transmission andreceiving means, compass and positioning utilities. The unitcommunicates with all other team members' units including a central unitusually with the team leader, giving the users a visual presentation ofall team members' position. All units have been allocated particularroles within the team and their current role is also displayed on otherteam members' units. The unit includes means for sending and receivingvarious messages to and from other team members, alarms and informationfrom both active and passive sensors available within the current team.

The control unit of the present invention can be similar to a generalteam unit, the only difference being that the control unit has aparticular role set, such as “team leader”, and may have a particularsymbol 511, such as the pentagon shown in FIG. 5. In a preferredembodiment the control unit is responsible for configuring theencryption for the team, i.e. to initiate distribution of the symmetrickey to be used. The control unit thus has stored, or the user enters,the public keys for all team members, whereas the team units, or theirusers, only need to know the public key of the control unit. In apreferred embodiment, the control unit also has a screen with resolutionsuitable for displaying maps, and the positions of the team units can beshown overlaying the map. The control unit may also have a more powerfultransceiver than a team unit, communication devices for sending andreceiving information outside of the team, an improved GPS receiver, adisplay with better resolution, and a device for text input to composemessage, rather than selecting predefined messages from the menu. Allunits are designed to be operational for more than 10 hours of constantuse, using re-chargeable 3.3v batteries with 1 Ah.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of team unit.

FIG. 2 is a front view of a team unit with four buttons.

FIG. 3 is an example communication flow in a team, with team units,central unit and sensors.

FIG. 4 is an example message format.

FIG. 5 is an example team unit display with alarm and out of boundsarea.

FIG. 6 is an example team unit display with waypoint.

FIG. 7 is an example team unit display with alarm message.

FIG. 8 is an example team unit display with bearing only.

FIG. 9 is an example team unit display on low resolution screen.

FIG. 10: Alarm displays indicating acknowledgement needed.

FIG. 11: An alternative embodiment of the team unit with six buttons.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a block diagram of a unit. A bus is used for communicationbetween the various modules. In a preferred embodiment, severaldifferent buses are used for interconnecting the modules: SerialPeripheral Interface (SPI) is used between the microcontroller andmemory. Philips I2C used between the microcontroller and the compass,UART [universal asynchronous receiver/transmitter] is used between themicrocontroller and the other modules. There are positioning and compassmodules for positioning information. In a preferred embodiment thepositioning module cannot be set in stand-by power mode by commands onthe communication bus, but rather by controlling the power to themodule. When the positioning module is turned on, it will remember itsformer settings and start searching for satellites based on thisinformation. The transceiver is used for data communication with otherteam members. The remote device controller is, for example, usingBluetooth or other suitable protocols for communication with sensors.The display shows the information, for example, on a screen, but couldalso be a head up visor or retinal display. The microcontroller runs thestate machine and memory is used both by the microcontroller, but alsofor storing messages and for logging positioning and sensor information,so that the unit may function as a black box where information can berecovered in case the unit's movement and sensor readings need to berecovered. The local input device controller is handling the use of thebuttons, but could also handle e.g. a touch screen or other inputdevices directly connected to the unit. Input devices such as a keyboardcan also be connected to the remote device controller, unique e.g.Bluetooth. To allow for optimized power saving abilities, each modulecan be controlled individually by reducing power consumption (forinstance by reducing power transmission) or being switched off.

FIG. 2 is an illustration of one embodiment of a team unit 200.According to this embodiment, the team unit has a screen 210 forpresenting information to the user, two buttons 220 for scrollingthrough user menu and two buttons 230 for navigating inwards or outwardsin the menu structure. The unit is designed for use under stressfulcircumstances and in hard conditions, with a simple and logicalinterface.

The team unit 200 has a built in position receiver used to receivepositioning signals and calculate the user's own position. Variouspositioning means could be used in the present invention, e.g. GPS,GALILEO, GLONASS, etc. In one embodiment, the position receiver is a GPSreceiver, for instance the LEA-5 from uBlox, that also supports GALILEO.In order to ensure optimal positioning signal strength, the antenna ismounted on the highest point of the unit. In this embodiment, the unitcan receive signals from up to 16 satellites at one time, ensuringoptimized accuracy of positioning data. Like all other electronics inthe unit, the positioning module is designed to work with minimum powerconsumption. The positioning unit is communicating with the team unitcontrol chip and radio transmission means for sending its own positionto all other team members.

In addition to the positioning module, the unit 200 also has a build incompass module. In one embodiment, the compass module is a digitalmagnetic compass module having 2 magnetometer sensors mountedperpendicular to each other. The two magnetic sensors register themagnetic field surrounding the two axes, representing the earth magneticfield if no other magnetic fields are present. While this particularcompass module requires the unit to be held in a horizontal positionwhen reading the information, other compass units may be used to betterensure reliable data at all times. The compass information is onlytreated when the unit is set to “compass information” mode.

The team unit can also be equipped with a short range radio device, likeBluetooth, for communicating with various sensors and the like. It couldalso be used to connect the team unit to other personal equipment, forinstance personal radio communication or sound devices.

The core of the unit is a microcontroller, specifically designed tooperate without the need of an operating system. This ensures better andsafer operating status, and a better protection against Electro MagneticPulse (EMP) attacks. Internal memory is used for logic and communicationcontrol, while at the same time giving the ability to store information,like, for instance, messages, waypoints and positioning log.

In one embodiment of the invention, all data received from thepositioning module as well as sensors connected to the unit are storedin the memory module. In order to optimize for detailed logginginformation or high performance (low power and memory consumption), thelogging update information could be adjusted accordingly (e.g. every 10seconds or every 1 minute). After completion of an assignment, theusers' movement and data from the sensors can be reviewed and evaluated.The complete session can be replayed, and the team can evaluate theirperformance based on accurate historical information. For trainingsessions or preparations for important missions, this feature canimprove the overall performance of the team, making them aware of theirmovements in relation to other team members as well as evaluate theimportance of information given from the sensors. In specific cases, forinstance if a fallen soldier has been identified at the battlefield, thelogging information could help explain the course of events. Bothinformation about his/her movement, and information from the sensors,could give valuable information.

In one embodiment, two memory chips are used, one for central storingand one for additional use if needed. The memory chips are responsiblefor storing messages received to the unit, predefined messages that canbe sent to the master unit, and received waypoints and other statusinformation. All memory chips and controllers are selected based ontheir low power consumption, reliability and number of connectionoptions. In one embodiment, the micro controller uses 3.3 V with a clockfrequency of 73,728 MHz for ensuring good output and to better complywith the frequencies used in serial communication.

In a preferred embodiment of the invention, the team unit is operatingusing a state machine running a continuous loop, thus it does not needany traditional operating system. The core of the software is a statemachine, always deciding what to be displayed and which next states arelegal. The compiled software from the implemented controllers andelectronic devices are loaded into a flash memory, and is automaticallyloaded when the unit is turned on. The state machine is running througha continuous loop, and certain modules are in operation at all times.Such continuously operating modules are, for instance, checking forbutton inputs, sending and receiving positioning information,registering communication between installed hardware etc. Both externalinformation, like pushing one of the four buttons, or internalinformation, for instance information from one of the implementedmodules, are deciding the next state.

As a state machine without an operative system, the unit is robust, andwill in case of an error condition restart and enter a valid state. Thisis achieved by having a counter that is reset in the main loop, called a“watch dog”, where reset is triggered if an error situation occurs.Error conditions can occur, for example, after the unit has been exposedto an Electro Magnetic Pulse (EMP).

For situations where it is necessary that information must be treatedimmediately, the system uses an interrupt message to stop the continuousloop. A bit flag is set to warn the system about an interrupt, and theinformation is treated accordingly. Such information could be input toturn off the button lock, GPS signal information or saving incoming datain the memory chip. When receiving positioning data, the data isvalidated using Cyclic Redundancy Check (CRC) to ensure that the dataflow is not corrupted. The data received from the positioning unit, likecurrent position, GPS clock and data, is then being analyzed and storedin the memory unit.

FIG. 3 shows a team with team units TU1 to TU4, a control unit CU, threesensors S1-S3 and two control units for other teams CUA and CUB. CUcommunicates with TU1 and TU2. Data, e.g. positioning information,alarms and sensor readings from TU3 and TU4 is relayed by TU2. As allunits in the team can both communicate directly and relay for otherunits, the position from TU3 is sent via TU2 to reach TU4. In order tostop propagation of messages in the team when using the relay function,a hop count flag can be set in the message header. For instance, themessage is only allowed to be relayed three times, setting the maximumhop count to three. In that case, when a relay message is received thehop count flag is decremented by one, and if larger than one the messageis relayed. If the hop count equals zero after being decremented, themessage will not be relayed further. In an alternative embodiment, timeinformation is used rather than hop count. A sensor can be connected toone or more units, as is shown for S2. In this preferred configurationof the system, only CU is allowed to communicate outside the team, andis here shown to communicate with the control units of two other teams,CUA and CUB.

In special situations or for saving battery power, it can be importantto transmit with as low a power as possible. In a preferred embodimentthe power transmitted varies between 10 and 500 mW, the latter giving arange of up to 6 km. In one mode of communication messages are normallysent as encrypted broadcast messages. FIG. 4 shows message formats,including how only parts of the message need to be encrypted. Ifmessages are not acknowledged, then the transmission power couldnormally be adjusted up. However, to transmit with low power, it ispossible to enter a communication mode, where other units are used asrelay, as shown in FIG. 3. The communication mode could be set from thecontrol unit, e.g. by sending a message indicating threat level, or byparticular alarm messages, such as a gas alarm. It is also possible toindicate the power level in the messages. In FIG. 4 is a message formatshown that uses half a byte to indicate the power level that has beenused for sending the message. Various schemes can then be used, e.g.starting to transmit with low power and stepping it up until a level isreached where the messages are acknowledged.

In the preferred embodiment, the protocol used for communication isbased on low power 8-bits microcontrollers, and are specificallydesigned to be optimized for low bit rates, high flexibility andallowing for large variation in message size and radio transmissionfrequencies. In addition, the protocol is designed for carrierindependent communication, meaning that the data can be sentindependently from underlying network structure. The protocol has threemain parts;

-   -   A generic data format encapsulating different types of messages    -   An acknowledge message, used in the systems reliability        mechanism    -   Different types of messages

In the message protocol, predefined message types are implemented, alsopresented in table 1.

TABLE 1 Size Acknowl- Message Content (byte) edgment Note Pos Longitude,9 No The unit's own position Latitude Text Text 0-245 Yes Free text orpredefined message BattStatus Battery 2 No Indicates battery statusstatus for attached Smart Battery AmmoStatus Ammunition 2 — statusCasualty Longitude, 9 Yes Indicates casualty or Report Latitude injuryat a given location Contact Longitude, 9 Yes Indicates hostile ReportLatitude detection from a given position Waypoint Longitude, 9 YesStored waypoint Latitude Poll Request for 2 No Used for requestinginformation information from team unit after a given message type (e.g.battery status or position) TeamPos Longitude, 10  No For relaying teamunits' Latitude, positions to units outside Pos-age of current team

In one embodiment of the invention, the following message types areimplemented; “Pos”—for sending team unit position to all team members,“Text”—predefined messages from the team unit or composed messages fromthe central unit, “BattStatus”—information about power status of theunit, “AmmoStatus”—information about the user's ammunition status,“Casualty Report”—injury or damage in a certain position, “Contactreport”—enemy contact from given position, “Waypoint”—stored waypoint,“Poll”—request for information (e.g. battery status, position etc.) and“TeamPos”—from central unit to other central units or above ranked unitsregarding current team position. Most of the messages includepositioning information from the sender, and at the same time somemessages require the respondents to acknowledge the reception of themessages with an “Ack” message. Although various specific messages havebeen presented here, the protocol is not limited to these message typesonly. Additional types can be added if needed.

FIG. 4 is illustrating one possible implementation of a messagestructure. The message could be an all-to-all message, for instancealarm message, a predefined message stored in the team unit, or variousstatus messages. When sending a message from the team unit, the messageheader is first assembled from the following fields; sender address,size of the data field, destination address, acknowledge flag andsequence number. The header, together with predefined preamble andverification fields are used to calculate the header check sum. Afterassembling of the header, data fields are added and the check sumcalculated. The message is then sent, and if the message requires anacknowledgement the message is queued until acknowledge is received fromthe recipients and then deleted from the message system. If noacknowledgment is required, the message is deleted immediately.

In one embodiment the messages are encrypted, using a common symmetricencryption method such as the Advanced Encryption Standard (AES). As themessages may be relayed by several units that need not read the contentof the message, the header is unencrypted. The AES key can bedistributed and changed using Public-key cryptography, where the privatekeys may be set in firmware for each unit, and the public keys ofpossible team units can be stored or exchanged when the units aredistributed to the team. The units may also communicate withoutencryption or they can have a default AES key to be used when an AES keyhave not been distributed using the Public-key cryptography. If aparticular unit is lost or compromised, a self destruct message could besent. Such a message could for instance inform the device to initiate anerasure of all vital information, and only transmit messages (forinstance position messages) unencrypted on an open channel. Thisprevents the lost unit from compromising the position and messageinformation sent between the other team members, while at the same timebeing able to keep track of the lost unit. In another embodiment, onlythe remaining units could update their symmetric encryption key (AESkey) and in that way avoid sending information to the compromised unit.

When receiving a message, the message header is first collected and thecheck sum is calculated and compared to the value in the header. If thecheck sum is not correct, the message is deleted. If the receiveridentification is not identical to the header destination or the messageis not a broadcast message, the message will be disregarded. If themessage is an acknowledge message, the sequence number is read and themessage is put in the out queue. If the message is a data message, itwill be stored in the internal unit memory. If the message is anacknowledgement message, the acknowledge message is produced based onsender address, sequence number and status, and then returned to thesender either automatically or when the user acknowledge that themessage has been read.

FIG. 4 shows different message formats. The topmost message format is asimple, unencrypted format. The middle message is the data part of amessage for positioning used when a unit reports its position. Inaddition this part has fields for vital sensor information, such asheart rate. The message at the bottom of the figure is a message forencrypted communication, where, for example, positioning data as shownabove, can be placed. The format allows several teams to operate on thesame radio channels, as the messages have address fields indicationdestination team and unit (DestinationL). The SessionID field indicateswhich AES key is used for the following encrypted part, and thus a unit,normally a control unit, may belong to more than one team.

In FIG. 3, an embodiment of the presented invention, the systemcomprises one central unit and one or more team units, with all-to-allor one-to-all communication. In addition, sensors can be connected tothe units e.g. using short range radio transmission (i.e. Bluetoothtechnology), sharing specific environmental information or informationabout the user of the team unit (i.e. heart beat or body temperature).The sensors can be active, such as a laser measuring distance or atriggered camera, or passive such as a heart rate sensor or a gasdetector. Sensors could be classified as passive or active. The passivesensors are sensors not relying on actions from a user in order to beactive. They are monitoring specific features continuously, for instancebio sensors or gas detection units. Active sensors are sensors operatedactively by a user, for instance a laser distance measurement device.All sensors could be operated by any user in the team, and thecommunication module in the unit makes it possible to transferinformation from one sensor to all members of the team.

The central unit also has the ability to send messages to other centralunits in different teams or to a higher ranked unit (for instance atroop command post). The messages could be positioning information, textmessages, alarms, pictures and other useful information, using a messagestructure and protocol similar to the one used in the present invention,or using another tactical communication system.

In order to show the information to the user, the unit is equipped witha small screen interface, for presenting information to the user havingboth text and simple graphics. The screen is designed with two backlight sources for ease of use and security reasons, one with traditionallight and one with infrared (IR) back light, the latter for use incombination with night vision equipment. In daylight, the display isreflecting available light, making it optimal for reading in sunlight.In order not to reveal the user's position, for instance to enemyforces, the display can be inverted in order to reduce the amount oflight to be radiated. The display brightness is adjusted using pulsemodule signals, turning the diode lights on and off with a highfrequency, e.g. a duty cycle of 1/250. Other methods for avoidingdetection could be used, e.g. different pulsing of light source,fluorescent backlight or night vision.

FIGS. 5 and 6 shows the display of a team unit. The unit itself isdisplayed in the middle as a circle with role information 510; the roleis here shown as G1, e.g. meaning first gunner. Another team unit isshown as G2, e.g. meaning second gunner. This team unit is displayed inred, indicating a gas alarm, from a sensor connected to this unit. Ascan be seen in FIGS. 7 and 10, alarms can also be indicated as messageson the screen. FIG. 7 shows an alarm displayed as an overlay message.This alarm does not indicate the need for acknowledgement, as the alarmsin FIG. 10. All positioning information is shown in relation to its ownposition and orientation. The circle 520 is a presentation of thecurrent range resolution, the current radius of the circle is presentedat the lower right corner of the screen; 530. Other team members' andsensors' positions are presented as small circles with information aboutthe current role of the unit. There are many other ways of presentingbearing and distance information on the display, e.g. by use of vectors,waypoints, distance information for all team member and symbols. Thescale of the display could also be dynamically changed, e.g. based onthe distance to the furthest unit, and this new scale could be indicatedby the distance.

FIG. 8 shows only the bearing to other units, and not the distance. Thisis useful, for example, if the team members are very close, or somemembers are far away. In this embodiment the lack of distanceinformation is indicated by the radius of the distance indicating circleshown as 0 m and the circle is dashed. There are other ways ofindicating that only bearing is displayed.

The possible roles can be predefined in a list in the menu, or theycould be freely set, e.g. by entering text for predefined roles ordefining new roles as the text is entered. A role serves severalpurposes: it may inform the other team members of duties and expectedbehavior, it may give certain rights to configure the system or sendalarms, or it may indicate the use of specialized sensors. Examples ofroles are: Machine Gunner, Gunner, Senior Fire Fighter, AuxiliaryFirefighter, Medic and Rescue Worker. Roles can be changed and a unitmay have more than one role. The roles could be changed on the unit inquestion or from the central unit, and there could be set of rulesdefining which changes are allowed.

The Central Unit is here shown as a black pentagon 511. Additionalgeographical information concerning the surrounding area could also besent to the team unit and presented in the display. Such informationcould for instance be “Out of bounds” areas 540; areas where the teammembers are specifically forbidden to enter (like mine fields etc.).When an alarm message is sent from one of the team units, all other teamunits are warned and the position of the unit sending the alarm ishighlighted in the display (G2). The display will always be oriented inthe same direction as the team unit, and based on range and angle to theother team members, the user will always be able to determine thecorrect position of all team members. A line indicating the direction toNorth or a predefined direction on the Earth is also displayed (550),ensuring that the team member is appropriately oriented to thesurrounding area.

A unit that has lost positioning information, e.g. from being inside abuilding, can be indicated on the team's displays with information onhow long the unit has been without positioning information or howuncertain the position is. The assumed position can be estimated by deadreckoning, and the uncertainty can be graphically indicated, e.g. byblurring the unit on the display.

FIG. 9 shows a display for a low resolution, monochrome display. Batterylevel and GPS reception level is indicated. An envelope indicates newmessages. A key indicates encrypted mode. Time is shown as 15:31. Thedistance to a waypoint is shown as 65 m and the R=50 m indicates thescale by giving the radius of the circle. The display is inverted, asnot to radiate more light than needed. Other team members are indicatedwith O, 1 and D.

In one embodiment, the menu structure in the team unit is designed to beoperated with four buttons. Two buttons are used for scrolling in themenu system, while the two others are used for selecting or deselectingthe different alternatives. FIG. 10 shows additional menu structures,and how the user is able to navigation by using the four buttonsavailable in the team unit. The menu system is designed to allow forquick access to specifically important messages, for instance enemycontact. These messages are referred to as set click messages. In oneembodiment, the right button could be used for selecting predefinedmessages directly. One click gives the user an overview of the messagemenu, the next click selects predefined messages, the third clickselects alarm messages and the fourth click sends an enemy contactalarm. In this way, the user is given the ability to select the messageenemy contact without having to look at the unit, while at the same timeminimize the chance of sending an alarm message unintentionally. In caseof enemy contact, the user can select the alarm message by clickingrapidly four times on the right button, without having to take his/herseyes of the enemy. Different menu structures and button combinationscould be used to allow for more than the one set click message describedhere.

FIG. 10 shows alarms that overlays the display. The right handindication of “forstått” (“understood” in Norwegian) is also anindication of which button to be used for a one-click acknowledgement ofreceipt.

In an alternative menu structure for a four-button team unit as of FIG.2, the scroll buttons 220 are used for scrolling in the choices asindicated and the right select button 230 is used for selecting.

FIG. 11 shows an embodiment of a team unit with six buttons. The twoside buttons operates as a single input command; both buttons need to bepressed to activate. This gives in effect a five button unit, but withadded confidence when using the fifth button, in that the two halves ofthe button are placed on adjacent sides of the unit. This button cane.g. be used for giving critical alarms such as enemy contact orreporting injuries.

What is claimed is:
 1. A system for tracking and communicating betweenunits in a team comprising: a plurality of portable team units, eachteam unit having: a GPS module; a compass module; a display showing theposition of the unit and positions of other team units; a passivesensor; a radio communication module, the module having a transmitterand receiver; a memory component for storing position information,alarms, and text messages; a handheld central unit having: a digitalmap; a display showing positions of team units on a map; and atransmitter and receiver sending and receiving text messages, positioninformation and alarms; the handheld central unit communicating withother team units, assigning each team unit at least one role, andcommunicating at least one message containing an instruction selectedfrom the group of: deleting information, turn on, turn off, and changepower consumption; and the system configured to use a hop counter ortime information to stop propagation of messages.
 2. The system as setforth in claim 1 having said communication in the system being selectedfrom a group of: open, encrypted and partially encrypted.
 3. The systemas set forth in claim 2 having said partially encrypted communicationbeing the payload of an encrypted message.
 4. The system as set forth inclaim 1 having said text messages being predefined or typed and selectedfrom a menu or set click messages.
 5. The system as set forth in claim 1having said units sending messages that require acknowledgement ofreceipt.
 6. The system as set forth in claim 1, wherein said units havea mode displaying information in a dark environment.
 7. The system asset forth in claim 6 having said mode using infrared backlight, pulsingof a light source, fluorescent backlight or night vision.
 8. The systemas set forth in claim 1 having said text message including a power levelvalue indicating the level of power of the message.
 9. The system as setforth in claim 1, wherein said units use active sensors.
 10. The systemas set forth in claim 1, wherein said compass module has an arrowpointing at a predefined direction.
 11. The system as set forth in claim1 having said display on the team unit showing an overlay of geographicinformation.
 12. The system as set forth in claim 11 having said overlayof geographic information being a marked out of bounds area or routeinformation.
 13. The system as set forth in claim 1 having said rolebeing chosen from a list.
 14. The system as set forth in claim 1 havingsaid role being set by entering text information of a predefined role.15. The system as set forth in claim 13 or 14 having said role beingchanged.
 16. The system as set forth in claim 1 having said display onthe units indicating that at least one unit has lost positioninginformation.
 17. The system as set forth in claim 1 having all distancesand bearings to other units displayed relative to said handheld centralunit.
 18. The system as set forth in claim 1 having said unitsdisplaying only bearings for some or all units.
 19. The system as setforth in claim 1 having said units store positioning log and sensorinformation.
 20. A device for tracking and communicating between unitsin a team comprising: a display showing position of the device andpositions of other units, the display showing all distances and bearingsto other units relative to said device; a plurality of buttons, theplurality of buttons including at least two or more buttons that requiresimultaneous activation; a positioning module; a compass module; atransceiver module; a memory component storing predefined messages; thedevice sending data directly or relayed between other units and sendingor receiving at least one message instructing at least one of thefollowing actions: deleting information, turn on, turn off and changepower consumption.
 21. The device as set forth in claim 20 having saiddisplay showing an overlay of geographic information.
 22. The device asset forth in claim 20 having a mode for displaying information in a darkenvironment, said mode using infrared backlight, pulsing of a lightsource, fluorescent backlight or night vision.
 23. The device as setforth in claim 20 having said predefined messages being one clickacknowledgement messages.
 24. The device as set forth in claim 20 havingan indicator showing the roles of the other units.